1. Field of the Invention
The present invention relates to an electrically heated chemical delivery system, and, more particularly, to a PTC electrical heater including a flexible printed circuit.
2. Description of the Related Art
A positive temperature coefficient of resistance (PTC) material exhibits the characteristic that, as the temperature of the material rises, the electrical resistance of the material also rises. If an electrical component is composed of PTC material, and if a voltage is applied to the component, the component will dissipate energy at a rate of V2/R where V is the applied voltage and R is the instantaneous resistance of the component. Unless sufficiently cooled, the PTC electrical component will heat up as a result of the dissipated energy and thereby increase the material resistance which will decrease the electrical current through the component and decrease the energy dissipation of the component. The PTC component is therefore somewhat self limiting from an electrical current point of view.
A Positive Temperature Coefficient (PTC) heater circuit applies an electrical potential on opposite sides of a PTC material to generate heat. As the temperature of the PTC material increases, the electrical resistance also increases. Typical PTC heater circuits use an insulating film and two metal electrodes in proximity to a heat sinking/distributive surface. Although this construction technique is effective to produce a properly operating PTC heater, it can be relatively expensive in terms of fabrication and assembly.
What is needed in the art is a PTC heater which is easily and cost effectively fabricated.